JP2008531851A - Electrical circuit for electrolytic cell and method for reducing electromagnetic field near electrolytic cell - Google Patents

Abstract

An electrical circuit for an electrolytic cell and a method for reducing the electromagnetic field in the vicinity of the electrolytic cell are provided.
An electrical circuit for reducing an electromagnetic field in the vicinity of an electrolytic cell includes an electrolytic cell, an electrical return line including at least one bus for returning current flowing through the electrolytic cell, and a waveform that is phased with respect to each other. And a power source with at least two rectifiers for delivering the off-current.
[Selection] Figure 1

Description

The present invention relates to an electrolytic cell, and more particularly to power supply of the electrolytic cell.
More particularly, the present invention relates to an electrical circuit for supplying a rectified current to an electrolytic cell having a bipolar electrode.

  In particular, the use of electrolyzers with bipolar electrodes that are supplied with direct current is common practice in the electrochemical industry. Such an electrolytic cell is widely used for electrolyzing an aqueous solution of sodium chloride for the purpose of producing an aqueous solution of chlorine, sodium hydroxide, or an aqueous solution of sodium chlorate.

  Due to the high current density employed in electrolyzers with bipolar electrodes, rectified AC (alternating current) current is generally used instead of DC (direct current) current. The rectified AC current usually has a pulse, which depends on the rectifier in which the frequency and amplitude are used. As a result, the electromagnetic field generated by the rectified AC current tends to generate an induced current in living organisms, and the strength of the induced current is the value of certain industrial applications, especially the continuous production of chlorine and sodium hydroxide aqueous solutions. Is relatively high in a bipolar electrolytic cell.

  Also, electromagnetic fields generated by high electromagnetic fields, especially rectified AC currents, can cause harmful consequences to the human body under extreme conditions due to induced currents that pose a risk of generating in the body. Are known. As a result, it is important to take measurements to protect personnel near the industrial facility or to reduce the strength of the electromagnetic field near the industrial facility. In addition, standards have been issued in this regard, demanding that the strength of electromagnetic fields in industrial premises be reduced. Among these standards, the European standard 89/391 / EEC is a particularly strict standard.

It is an object of the present invention to provide an electrical circuit of a novel design for supplying a high intensity current to an industrial electrolytic cell.
In particular, it is an object of the present invention to provide an electrical circuit that reduces the electromagnetic field near the electrolytic cell to a sufficiently low value in order to comply with the above-mentioned European standards.
More particularly, it is an object of the present invention to reduce the magnitude of the electromagnetic field in a passage extending along the side wall of an electrolytic cell having bipolar electrodes.

  Accordingly, the present invention relates to an electrical circuit for reducing the electromagnetic field in the vicinity of an electrolytic cell, an electrolytic cell, an electrical return with at least one bus bar for returning the current flowing through the electrolytic cell, and a waveform And a power supply by means of at least two rectifiers (5a, 5b), preferably connected in parallel, for sending currents that are out of phase with respect to each other. The electrical circuit according to the invention is advantageously fed with a three-phase AC current.

  The rectification of the three-phase AC current sends a current having a base frequency whose vibration is six times higher than the base frequency of the three-phase current (eg, six times 50 Hz). The use of at least two rectifiers that are out of phase with respect to one another according to the invention makes it possible to increase the frequency. The electrical circuit according to the invention, in which the strength of the current and the specific configuration are associated with the electrolytic cell, makes it possible to substantially reduce the electromagnetic field radiated in the vicinity of the electrolysis installation.

  In one advantageous embodiment of the electrical circuit according to the invention, the electrical circuit comprises two rectifiers with a phase shift between 29 ° and 31 °, preferably close to 30 °. In this embodiment, a current is obtained having a base frequency that is twelve times higher than the base frequency of the unrectified three-phase current.

  The present invention is particularly applicable to an electrolytic cell having a substantially vertical bipolar electrode. Such electrolyzers are well known in the art and are widely used for electrolyzing aqueous solutions of metal halides, especially sodium chloride. The electrolyzer is generally formed by a series of metal frames each containing a bipolar electrode, which are juxtaposed like a filter press (Modern Chlor-alkali technology, Volume 3, SCI, 1986, chapter 13 “Operational Experiments Obtained in Bipolar Hoechst-Uude Membrane Cell” Modern Chlor-alkai technology, Volume 4, SCI, 1990, chapter 20 “Hoechst-Uude Single-Element Membrane Electrolyzer: Overview-Experiment-Application”). The metal frame usually has a square or rectangular outer shape, and the metal frame is juxtaposed like a filter press to form the upper, lower or bottom wall of the electrolytic cell and two side walls.

  In a preferred embodiment of the electrical circuit according to the invention, the electrical circuit further comprises at least one drain coil coupling the outputs of the at least two rectifiers. The purpose of the drain coil is to establish an anti-parallel reactance between the outputs of the rectifier. The drain coil is advantageously formed by combining iron plates and sheets to limit heating losses. The output of the rectifier passes through the drainage coil in opposite directions, and a current perturbation present in one output causes a reverse perturbation in the current from the other output. When the two outputs are superimposed, the result is a total current that is not so perturbed.

  In another preferred embodiment of the electrical circuit according to the invention, the electrical return consists of at least one bus bar arranged below or above the electrolytic cell. The choice of placing the bus bar below or above the cell is determined by considering the cell structure and the mode of assembly of the bipolar electrode. As a modification, the above-described electrical blanking line may include one bus bar disposed below the electrolytic cell and the other bus bar disposed above the electrolytic cell. In another variation, the electrolytic cell may also include a plurality of bus bars under the electrolytic cell and a plurality of bus bars above the electrolytic cell. In practice, in view of both electrolyzer assembly and maintenance, the electrical return described above should generally not include a bus bar above the electrolyser.

  If all other conditions are the same, the electrical circuit according to the present invention is mainly used along the side walls of the electrolytic cell with bipolar electrodes, in the vicinity of the electrolytic cell, especially in the path used by operation and maintenance personnel. Was found to be substantially reduced.

  In the electrical circuit according to the invention, the material of the busbar is not important for the definition of the invention. The bus bar is generally made of copper, aluminum, or aluminum alloy.

  In the electrical circuit according to the invention, the outline of the cross section of the busbar is not important for the definition of the invention. For example, the outer shape may be a square, a rectangle, a circle, or a polygon.

  In one particular embodiment of the electrical circuit according to the invention, the busbar is oriented so that it has a rectangular outline and its large surface is substantially horizontal. If all other conditions are the same, minimize the size of the electromagnetic field in the vicinity of the electrolytic cell by selecting a rectangular busbar placed horizontally under and / or above the electrolytic cell Was observed. It was also observed that the smaller the ratio of thickness to busbar width, the greater the decrease in electromagnetic field near the electrolytic cell. As a result, it is preferable to use a flat metal plate for the bus. As a variant, it is possible to use a plurality of flat metal plates arranged side by side below and / or above the electrolytic cell.

  In addition, if all other conditions were the same, it was also observed that the electromagnetic field magnitude near the electrolytic cell was reduced when the busbar was placed near the electrolytic cell wall.

  As a result, in another particular embodiment of the electrical circuit according to the invention, the bus bar is located in the immediate vicinity of one wall of the electrolytic cell. In this embodiment of the invention, the wall of the electrolytic cell is the lower or bottom wall or the upper wall of the electrolytic cell, depending on whether the bus bar is positioned below or above the electrolytic cell. In this embodiment of the invention, the expression “in the immediate vicinity of the cell wall” means that the distance between this wall and the busbar is at most equal to 5 times the busbar thickness (preferably 3 times). Means. This distance preferably does not exceed the thickness of the busbar.

  In a preferred variant of the above-described embodiment of the present invention, a bus bar is attached to the wall of the electrolytic cell. In a variant of this preferred embodiment of the invention, the bus bar advantageously has a thickness of electrical insulation necessary to separate the bus bar from the wall, one of the large faces being flat with the wall attached. Metal plate. A flat metal plate may be attached to a portion of the wall surface area. A flat metal plate is preferably attached to almost all of the surface area of the wall.

  In yet another specific embodiment of the present invention, the electrical return described above further includes two additional bus bars located in the immediate vicinity of the two respective sidewalls of the cell. In this embodiment of the invention, the expression “nearby” is consistent with the definition given above for this expression.

  If all other conditions are the same, the presence of the additional bus bar reduces the magnitude of the electromagnetic field near the electrolytic cell.

  In this embodiment according to the invention, the additional busbar may have any shape that matches the structure of the electrolytic cell. For example, the additional busbars may have a square, rectangular, polygonal, elliptical or circular outline. Further, the additional bus bars may have the same outer shape or different outer shapes, and the additional bus bars may have the same dimensional shape or different dimensional shapes. In practice, however, the additional bus bars preferably have the same outer shape and the same dimensional shape. Also, the additional bus bar preferably has a rectangular outer shape, and the additional bus bar is attached to each of the two side walls of the electrolytic cell via its large surface.

  In the embodiment of the invention that has just been described, the dimensions of each additional bus bar and the dimensions of each bus bar located below and / or above the electrolyzer ensure that the current is distributed within all bus bars. Determined by the method. In general, the current strength of the bus bars located below and / or above the electrolytic cell is preferably at least 5 times higher than the current strength of each additional bus bar.

  In yet another embodiment of the invention, which is particularly advantageous, the electrical return of the electrical circuit is arranged to generate an electromagnetic field that is substantially symmetrical with respect to the vertical midplane of the cell. In this embodiment, the desired objective (generating an electromagnetic field that is substantially symmetric with respect to the vertical midplane of the cell) is achieved by sizing and positioning each bus bar in an appropriate manner. The selection of the optimum dimension shape and the optimum position is determined by a person skilled in the art, in particular by the shape and dimension shape of the electrolytic cell. In practice, this result is generally obtained by arranging the bus bars symmetrically with respect to the vertical intermediate plane of the cell.

  In a last advantageous embodiment of the invention, the secondary electrical circuit is arranged in the vicinity of the primary electrical circuit. Current flows in the opposite direction in the secondary electrical circuit to produce a magnetic field that at least partially cancels the magnetic field produced by the current flow in the primary electrical circuit. Therefore, the secondary electrical circuit must be able to pass a current having a strength close to that of the current flowing through the primary electrical circuit. In order to obtain good compensation of the electromagnetic field, the secondary electrical circuit must be placed as close as possible to the primary electrical circuit. Considering the structural requirements that may require the two electrical circuits to be spaced at a point, a portion of the secondary electrical circuit is attached to the electrolyzer to obtain optimum electromagnetic field compensation. And preferably it is recommended that another part is also attached to the busbar. It is possible to feed the secondary electrical circuit by means of the power supply for the primary electrical circuit via the adjusting resistor. However, it is recommended that at least a portion of the secondary electrical circuit in the vicinity of the electrical return is fed separately.

  It is also recommended that a portion of the electrical circuit located between the rectifier and the electrolytic cell be configured to minimize the magnetic field. In general, it is recommended to place the current source and the electrical return as close as possible to each other.

  The electrical circuit according to the invention is particularly applicable to electrolyzers for the continuous electrolysis of aqueous solutions, such as water or aqueous alkali metal halide solutions, in particular aqueous sodium chloride solutions. As a result, in a preferred embodiment of the invention, the electrolytic cell includes a conduit for continuous intake of aqueous electrolyte and a conduit for continuous discharge of aqueous electrolyte.

  The present invention is particularly applicable to an electrolytic cell for the production of sodium chlorate by electrolysis of an aqueous sodium chloride solution. The present invention is particularly well applied to electrolyzers for the production of hydrochloric acid and sodium hydroxide aqueous solutions by electrolysis of aqueous sodium chloride solution, which selectively selects cations interposed between the bipolar electrodes. Includes a permeable membrane.

  The electrical circuit according to the invention applies to any electrolysis installation having at least one electrolytic cell with vertical bipolar electrodes.

  As a result, the present invention also relates to an electrolysis facility comprising at least one electrolyzer having a bipolar electrode, the electrolysis facility being connected to an electrical circuit according to the present invention. The electrolytic equipment according to the present invention may include a single electrolytic cell or a plurality of electrolytic cells electrically connected in series.

  The invention relates in particular to the use of this electrolysis facility for the production of chlorine and aqueous sodium hydroxide.

  The electrical circuit according to the invention substantially reduces the electromagnetic field in the vicinity of an electrolytic cell, in particular an electrolytic cell with bipolar electrodes.

  As a result, the present invention is also a method for reducing the electromagnetic field in the vicinity of an electrical circuit including an electrolyzer and an electrical return for returning current, the electrical circuit having a waveform, preferably 29 °. It also relates to a method powered by at least two rectifiers for delivering currents that are out of phase with respect to each other by ~ 31 °.

  In a preferred variant of the method according to the invention, the electrical circuit further comprises at least one drain coil coupling the outputs of the at least two rectifiers.

In the method according to the invention, the electrical circuit is also advantageously in accordance with various other embodiments of the electrical circuit according to the invention.
In the drawings, the same components are denoted by the same reference symbols.

  The electrolysis facility shown schematically in FIG. 1 includes three electrolyzers 1, 2, 3 designed to produce chlorine, hydrogen and sodium hydroxide by electrolysis of an aqueous solution of sodium chloride. The electrolytic cells 1, 2, and 3 are of the type having vertical bipolar electrodes. The electrolytic cell is formed by juxtaposing vertical rectangular frames 4 each containing vertical bipolar electrodes (not shown). The frames 4 are juxtaposed like a filter press. A membrane selectively permeable to cations is interposed between the frames 4 to define every other array of anode and cathode chambers. The anode chambers of the electrolyzers 1, 2, 3 communicate with a conduit (not shown) for continuous intake of an aqueous solution of sodium chloride. Further, the anode chambers of the electrolytic cells 1, 2, and 3 communicate with a header (not shown) for continuous discharge of chlorine. The cathode chambers of the electrolyzers 1, 2 and 3 communicate with two headers (not shown), which serve on the one hand for the continuous extraction of hydrogen and on the other hand for the continuous extraction of an aqueous solution of sodium hydroxide. Each role.

  The electrolyzers 1, 2 and 3 on the one hand include a bus 6 interposed between the electrolyzers 1, 2 and 3 and, on the other hand, an electric return line 7 which is arranged away from the electrolyzers 1, 2 and 3 The circuit couples the two rectifiers 5a and 5b in electrical series via the drain coil 19. The rectifiers 5a and 5b are fed by the AC current source 18 with a phase shift of 30 °.

In the electrolysis facility shown in FIG. 1, the electric blanking line 7 is composed of a long bus bar extending along one vertical side wall of the electrolytic cells 1, 2, 3. In the electrolysis facility schematically shown in FIG. 1, each of the electrolyzers 1, 2, and 3 includes, for example, 30 to 40 individual electrolysis cells, and the power source has a current ranging from, for example, 8 to 20 kA. Including a 520 VDC rectifier. This produces an anode current density ranging from 2.5 to 6 kA / m ² of anode area, depending on the electrode area. However, these numbers are merely representations and do not limit the scope of the invention and the claims.

  When the bipolar switch is closed, the rectified current is sequentially passed through the bipolar electrode in the electrolytic cells 1, 2 and 3 to the electrical return line 7. This current generates an electromagnetic field in the environment of the electrolysis facility.

  According to the present invention, the secondary electrical circuit including the segments 17a, 17b is arranged in the vicinity of the electrolytic cell and in the vicinity of the electrical blanking.

  The electrolytic installation schematically shown in FIGS. 2 and 3 represents one specific embodiment of the present invention, in which no secondary electrical circuit is shown. In these figures, only the electrolytic cell 3 is shown. In the electrolysis facility shown in FIGS. 2 and 3, the electric blanking line 7 includes two bus bars 9 and 10 disposed under the lower wall 11 of the electrolytic cell 3. The bus bars 9 and 10 are prismatic bus bars made of metal (preferably copper or aluminum) which is a good electrical conductor. These bus bars are objectively arranged on both sides of the vertical intermediate plane XX of the electrolytic cell 3. The bus bars 9 and 10 are also arranged near the lower wall 11 of the electrolytic cell 3. The effect of arranging the bus bars 9, 10 in the manner shown in FIG. 3 is that the electromagnetic field along the passage 12 extending along the side wall 13 of the electrolytic cell 3 and for operating personnel of the electrolytic cell 3 It is to reduce the size.

  If all other conditions were the same, it was observed that the strength of the electromagnetic field along the passage 12 was further reduced when the bus bars 9, 10 were close to the vertical midplane XX and the lower wall 11. It has also been observed that the magnitude of the electromagnetic field along the passage 12 can be reduced by reducing the ratio of the thickness to the width of the bus bars 9,10. Therefore, it is preferable to use a horizontal plate or sheet for the bus bars 9 and 10.

  In the embodiment shown in FIG. 4 where the secondary electrical circuit is not shown as well, the electrical return line 7 is a flat surface attached to the lower wall 11 of the electrolyzer 3 and covering substantially all the area of this wall. A metal plate or sheet 14 is included.

  In the electrolysis facility shown in FIG. 5, the electric return line 7 has two additional metal plates 14 attached to the lower wall 11 of the electrolytic cell 3 and two additional side walls 13 extending along the two side walls 13 of the electrolytic cell 3. Bus lines 15 and 16. The two additional bus bars 15, 16 are advantageously flat metal plates or sheets attached to the side wall 13.

It is a top view which shows the general structure of the electrolysis installation of one specific embodiment of this invention. FIG. 3 is a longitudinal schematic view of another specific embodiment of an electrolysis facility according to the present invention. FIG. 3 is a longitudinal sectional view taken along a plane III-III in FIG. 2. FIG. 4 is a view similar to FIG. 3 of another embodiment of the electrolysis facility according to the present invention. It is a preferable modification of the electrolysis equipment of FIG.

Explanation of symbols

1, 2, 3 Electrolyzer 4 Vertical rectangular frame 5a, 5b Rectifier 6 Bus 7 Electric return 17a, 17b Segment 18 AC power supply 19 Exhaust coil

Claims (14)

An electric circuit for reducing the electromagnetic field in the vicinity of the electrolytic cell (1, 2, 3),
An electrolysis cell, an electrical circuit (7) comprising at least one bus for return of the current flowing through the electrolysis cell, and at least two rectifiers (5a, 5) for sending currents whose waveforms are out of phase with respect to each other 5b) and a power supply.   The electrical circuit of claim 1, wherein the current is out of phase between 29 ° and 31 °.   The electrical circuit according to claim 1 or 2, further comprising at least one drain coil (19) coupling the outputs of the at least two rectifiers.   Electrical circuit according to any one of claims 1 to 3, characterized in that the bus bars (9, 10, 14) are arranged below and / or above the electrolytic cell (3).   Electrical circuit according to claim 4, characterized in that the bus bar (14) is attached to the wall (11) of the electrolytic cell (3).   6. The electric circuit according to claim 5, wherein the wall is a bottom wall (11) of an electrolytic cell.   Electrical circuit according to claim 4 or 5, characterized in that the bus bar is a flat metal plate (14), one of the large surfaces of the metal plate being attached to the wall (11).   The electrical line (7) further comprises two additional busbars (15, 16) attached to two respective side walls (13) of the electrolyzer (3). Electrical circuit.   The electrical circuit (7) is arranged to generate an electromagnetic field that is generally symmetrical with respect to the vertical intermediate plane (XX) of the electrolytic cell. The electrical circuit described.   The electric cell according to any one of claims 1 to 9, wherein the electrolytic cell includes a conduit for continuous intake of the aqueous electrolyte and a conduit for continuous discharge of the aqueous electrolyte. circuit.   The electric circuit according to claim 10, wherein the electrolytic cell includes a membrane that selectively transmits cations interposed between the bipolar electrodes.   The second electric circuit is arranged in the vicinity of the electrolytic cell (1, 2, 3) and the electrical return line (7) so that the current flows in the opposite direction to the current flowing in the electrolytic cell. The electric circuit according to claim 1, wherein the electric circuit is characterized.   A method of reducing an electromagnetic field in the vicinity of an electric circuit including an electrolytic cell (1, 2, 3) and an electric return line (7) for returning a current, wherein the electric circuit Said method, characterized in that it is fed by at least two rectifiers (5a, 5b) for sending out-of-phase currents, said rectifiers being connected in parallel.   14. The method according to claim 13, wherein the electrical circuit further comprises at least one drain coil (19) coupling the outputs of at least two rectifiers (5a, 5b).

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